Afterburner fuel metering device for turbojet engines



2,828,606 AFTERBURNER FUEL METERING DEVICE FOR ''URBOJET ENGINES FiledNov. 18, 1950 R. J. COAR April l, 1958 6 Sheets-Sheet 1 x25.. man

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Nh n AGENT R. J. COAR April 1, 1958 AFTERBURNER FUEL METERING DEVICE FORTURBOJET ENGINES 6 Sheets-Sheet 6 Filed Nov. 18. 1950 INVENTOR RICHARDJ. COAR AFTERBURNER FUEL METERING DEVICE FR TURBOJET ENGINES Richard l.Coar, Hartford, Conn.,

Aircraft Corporation, ration of Delaware Application November 1S, 1950,Serial No. 196,423 1 Claim. (Cl. 60-39.28)

assigner to United East Hartford, Conn., a corpo- This invention relatesto a fuel meter and in particular to a fuel meter for use with aturbojet engine having an afterburner for metering fuel to theafterburner.

An object of this invention is to provide a fuel meter l which willproportion fuel flow in accordance with one variable and vary saidproportion in accordance with a second variable.

Another object of this invention is to provide an afterburner fuel meterwhich will proportion afterburner fuel llow in accordance with an engineoperating vari-able and vary said proportion in accordance with anengine operating variable which varies as a function of afterburner fuelflow.

Further objects and advantages will be apparent from the followingspecification and drawing.

Fig. l is a schematic view of a. turbojet engine having an afterburnershowing the controls for the afterburner with a fuel meter.

Fig. 2 is an enlarged view in cross-section of the fuel meter includedin Fig. l.

Fig. 3 is a schematic view of a turbojet engine having an afterburnershowing the controls for the afterburner with a modification of a fuelmeter.

Fig. 4 is an enlarged View in cross-section of the modication of thefuel meter included in Fig. 3.

Fig. 5 is a schematic view of a turbojet engine having an afterburnershowing the controls for the afterburner with another modification of afuel meter.

Fig. 6 is an enlarged View in cross-section of the fuel meter includedin Fig. 5.

The turbojet engine 2 has a compressor 4, which, in the arrangementshown, is a centrifugal type, driven by a turbine 6. Combustion chambers8 therebetween deliver air from the compressor to the turbine. Anafterburner 10 is attached at the turbine outlet to provide a means ofincreasing the thrust.

The engine 2 has two axially-spaced annular intake openings 12 to directthe incoming air into the two oppositely facing annular compressorinlets. Compressed air discharging from the compressor 4 passes to theturbine through the combustion chambers 8 Where it is mixed with fuelfrom fuel nozzles 14. These fuel nozzles 14 receive fuel from thegovernor 15 through conduit 20. The fuelair mixture is initially ignitedwithin the combustion chambers 8 by a spark igniter 16. The governor 15maintains the rotative speed of the turbine rotor assembly in accordancewith the value selected by the power lever 17 by controlling fuel owsupplied through conduit and nozzles 14 to the combustion chambers 8.

From the turbine, the gases pass around a cone 18 into the diffusersection 19 of the afterburner. When the afterburner is operating, fuelis discharged into these gases from a plurality of fuel nozzles 26located radially in the diffuser 19. Since the gases leaving the turbine6 contain considerable unburned oxygen, the additional fuel introducedby fuel nozzles 26 provide a combustiblefmixture which may be initiallyignited within combustion chamber 27 by ignition means hereinafterdescribed, which An opening 135 connects annular groove 128 to a by-pass.ing of this combustible mixture is may be the type shown and claimed inthe co-pending applications Serial No. 196,402 filed November 18, 1950,now Patent No. 2,780,055, issued February 5, 1957, and Serial No.196,426 tiled November `18, 1950. The burnstablized in afterburnercombustion chamber 27 by ameholders 30 and 32. The

burned gases discharge from the engine through the nozzle 44 whose areacan be varied.

The variablev nozzle 44 operates between a minimumV opening for engineoperation Without afterburning'and a maximum opening for operation ofthe engine with afterburning. A nozzle and actuating system, similar tothe one shown with this invention, is shown and claimed in co-pendingapplication Serial No. 193,734 led November 2, 1950, now Patent No.2,714,285 issued August 2, 1955'. The. actuating system consists of thecylinder 130, piston 132, connecting control rod 134, nozzle control rod78, piston rod 13S, a car 140, and said car. Y

The afterburner control system can be divided into three main parts.They are the following: (l) the fuel system, (2) the ignition means and(3) the exhaust nozzle actuator control. These three parts are closelycoordinated by fluid conduit connections and an-electrical system.

The fuel system consists of the fuel tank 46, the fuel booster pump 48,the fuel pump 50, the fuel meter (see Figs. 2, 4 and 6) and the fuelnozzles 26. The fuel booster pump 4S is mounted on the fuel tank 46 andisy pump 50, by conduits 54 and 56.

connected to the fuel The fuel pump 50 is of the turbine type having aturbine rotor 58 mounted therein With an intake passage 60 and exhaustpassages 62 for the working fluid. The working fluid, which is shown Tascompressed air supplied from the compressor outlet of the engine,\isdelivered to the intake passage 60 by conduits 230, 64 and 66.` A motoroperated valve 68 is located at the junction of conduits 64-and 66 tocontrol the operation of the fuel pump by regulating the ow ofcompressed air tothe pump. The turbine This fuel meter has a housingV104 which contains there#v 1n four main parts; a metering orifice 106,a valve assemthe measurement of engine fuel bly 108for attenuating flowin accordance with turbine discharge temperature, a by-pass valveassembly 110, and a by-pass valve controlling mechanism 112. These partsare interconnected by passages and connected to other devices in theoverall system to provide an operative structure. `Afterburner fuel isadmitted to housing 104 through an opening 114 in a cover to a chamber116 which is connected t0 a fuel outlet passage 11S by metering orice106. A

normally closed solenoid operatedrvalve is-locatedV between passage 118and conduit 74. A filter be provided in inlet chamber 116 to lter outpurities in the fuel. which a conduit may fluid to another device.

The by-pass valve assembly 110 has a sleeve 124 xedly mounted in bore126 of housing 123 may Opening 121 provides a pointat be connected toYcarry a Working ond annular groove 133 is located at one end of Ybore126.A

Patented Apr. 1,1958' a track mechanism 142 for any? im- 104. AnannularV groove v 128 located between the ends of the `bore 126communi-Y` cates with the interior of the sleeveby slots131. -A`secV f2,828,606 o A Y.

fuel return conduit 137, Passages 139 and 192 connect the'endsfof thesleeve 124w with inlet chamber 116.

rA by-pass valve 141 is slidably mounted in sleeve 124. The end of thevalve 141 within the sleeve 124 seats against a conical ange143 at oneend of the sleeve 124, and 'ai conical flange 144 on the Avelve 141seats on the other end ofthe sleeve 124. The lby-pass valveV has apassage 146 therethrough connecting passage 139 to a chamber 194,hereinafter described. A bushing 166 with a restricting orifice 168 isprovided in one end of passage 146 and a bushing V160 with a iilter 162is provided at the other end.

An annular ring 170 is held between the housing 104 andfa cover '172which is held on by bolts 174. The'ring 170 hasan annular flange 176which forms a circular springseat for a spring 178 which is locatedaround valve 141 and has itsother end seated against ange 144 therebybiasing valve 141 toa closed position.

` A bellows 181 is tixed at one end to the inner diameter of-annularring 170 and at its other end to a washer member182 which is'mountedaround one end of valve 141. Two nuts 184 and 186 position washer member182 on valve 141. The interior of the bellows incombination with annulargroove 133, valve 141, bushing 182, ring 170, and the end of sleeve 124,forms a chamber 188 which is connected to inlet chamber 116 by passage192.V The exterior of the bellows 181, cover 172, ring 170, washermember 182, and end of valve 1411 form a chamber 194 which is connectedto a valve 196 of the by-pass valve controlling mechanism 112 bypassages 198, 200, 202, and 204.

The by-pass valve controlling mechanism 112 consists of a Walking beam`206 having various Vforceskapplied to regulate valve 196. A cover 208encloses this mechanism forming a chamber 209 which is connected to alow reference pressure by opening 211 and conduit 213. The walking Vbeamis pivoted'at 210. t Valve 196 consists of a bushing 212 iiXed inhousing 104 having an orice 214therein and a flow regulating part 216tixed on walking beam 206. y

AV spring 218,V mounted between two spring retainers 220 and 222 islocated under valve 1967to bias said valve to a closed position. Anadjustable screw v224 is mounted in abushing 226 llixed to cover 208 tomovably position spring retainer 220.

A cylinder 228 is-lixed to housing 104by bolts 232 with a diaphragm 234therebetween to preventleakage. Apassage 240 connects chamber 116 to oneside, of'diaphragm 234. Fluid pressure in passage 240 is applied throughdiaphragm 234 toa piston 236, which is interposedbetween the diaphragmand an adjustable. stop-238 on walking beam 206, to move the valve 196to an open position. A second cylinder 242 is xed to housing 104 bybolts 244 with Ya 'diaphragm 246 therebetween to prevent leakage. Apassage252 conneetspassage118to one side of Vdiaphragm 246. Fluidpressure in passage 252 isapplied through diaphragm 246 to a piston248;. which isinterposed betweenl the diaphragm and an adjustable stop'250 on walking beam 206, to move the valve 196 vto a closed position. Athird cylinder 254 is fixed to housing 104 by bolts .2564 with aAdiaphragm ZSStherebetween to prevent leakage. A passage 268 connectschamber 292, to be described later, to one sideof diaphragm 258.Fluidpressure in passage 268 is-applied through diaphragm' 2548 to apiston 260, which is interposed between the diaphragm `andan adjustablestop 264 on walking beam k206, to move the valvev 196 to a closedposition.

The attenuating valve assembly 108 has a sleeve 270 which is fixed inbore 272 of housing 104. Snap ring 274 holds a valve 275 of the assemblyin the sleeve. An annular groove 276 in the valve is connected to drainby passage 278. Valve 275 has an annular groove 280 which is connectedby openings 282 to an annular groove 284 in sleeve 270, which is in turnconnected to passage 286.y Passage 286 is connected through conduit 287and conduit to engine fuel nozzle pressure. A contour 288 formed on thelower face of groove 280 cooperates with an oriiice 290 to vary theopening presented through the orifice between two limits. This orificeenters into chamber 292 which is in turn connected by passage 268 topiston 260, and by passage 294, in which a restricting orifice 296 ismounted, to a reference fuel pressure conduit 298. Valve 27S is rotatedby a shaft 273 to vary the restriction formed by contour 288 and orifice290.

The fuel meter in Fig. 4 meters fuel ow as a function of engine air flowand this fuel ow may be attenuated manually or automatically to controlsome engine performance variable such as turbine discharge temperature.

This fuel meter has a housing 302 which contains therein four mainparts; a metering valve assembly 304, a metering valve controllingmechanism 306, a valve assembly 308 for attenuatng the measurement ofengine air ow in accordance with turbine discharge temperature, and atay-pass valve 310, these parts are interconnected by passages andconnected to other devices in the overall system tofprovide an operativestructure. Afterburner fuel is admitted to housing 302 through passage312 to metering valve 304. It is then metered by the valve and passedout opening 314 to a shut-olf valve 316. A by-pass valve 310 connectspassage 312 to conduit 54 thro-ugh conduit 318.

The metering valve assembly 304 has a sleeve 320 fixedly mounted in bore322 of 4housing 302. An annular groove 324 located between the4 ends ofthe bore 322 communicates with an annular groove 326 on the interior ofthe sleeve by bolts 328. A passage 330 connects the bottom of sleeve 320to opening 314 and passage 332 connects the top of the sleeve to opening314.

A metering valve 334 is' slidably mounted in sleeve 320 by ribs 336. Theend of the valve in sleeve 320 seats against a contoured circular ange338 at one end ofthe sleeve 320 and, a contoured circular ange 340 onthe valve seats on the other end of the sleeve 320. A hollow stem 342 onthe valve 334 extends upward through a hole 344 in a rigid disk 346,which is held between housing 302and member 348, to be connected withthe metering valve controlling mechanism.

The metering valve controlling mechanism 306 has a diaphragm 350 whichis held at its outer edge between member 348 and member 352. Valve stem342 is internally threaded and receives a hollow bolt member 354 whichpasses through a cup member 356, the center of diaphragm 350 and awasher 358 to hold these parts together.

A bellowsV 360 is connected at one end around valve stern 342 to washer358 and at the other end to the edge ofthe hole 344 in'rigid diskY 346.A chamber 362 is formed betweenV bellows 360, diaphragm 350, rigid disl:346 and member 348.

A second bellen/S364 is attached at one end to the head of bolt 354 andYat the other end to a plate 366 which is held between member 352Y andcover 368. A chamber 370 is formedbetween bellows 364, diaphragm 350,plate 366 andy member 352. A spring 372 is located'around bellows 3641between plate 366 and cup 356 acting in a direction `to` close valve334.

Chamber 3701s connectedto conduit 371 by opening 374,"and chamber 362 isconnected to the attenuating valve assembly 308 by passage 376. Theinterior of bellows 364 iis connectedto the outlet side of valveassembly 304 by passage378, which passes through bolt 354, hollow stem.342, and holes 382 in stem 342. The interior of bellows 360 is connectedto the outlet side of valve assembly 304l by hole 344y inrigid disk 346.

F[ 'he attenuating valve assembly 308 has a sleeve 384 which is fixed inboreA 386k olthousing 302. Snap ring 38S holds valve 390 of theassemblyY in sleeveV 384. Sleeve 384 has an annular groove 392 whichconnects passage 394which has a bushing 396 with an orifice 397 topassage 376. Passage 394 is connected through conduit 395 to compressordischarge pressure. An orice 398 connects annular groove 392 to thecenter of sleeve 384. The lower end of valve 390 provides the valveaction by a contour 400 thereon which varies the opening presented byorice 398. The end of sleeve 384 is connected by passage 402 and conduit404 to compressor inlet pressure. Valve 390 is rotated by a shaft 391 tovary the restriction formed by contour 400 and oriice 398. Y

A valve seat 406 is placed in opening 408 which connects passage 312with the by-pass fuel outlet 410. A valve sleeve 4t2 s ixedly mounted inhousing 302. By pass valve 414 is slidably mounted in sleeve 412 beingbiased against seat 406 by a spring 416. The chamber 418 formed by valve414 and sleeve 412 is connected to passage 332 by passage 420.

The fuel meter in Fig. 6 meters fuel flow as a function of engine airflow and this fuel ow may be attenuated manually or automatically tocontrol some engine performance variable such as turbine dischargetemperature.

This fuel meter has a housing 450 which contains therein four mainparts: a metering orice 452, a valve assembly 454 for attenuating themeasurement of engine air ow in accordance with turbine dischargetemperature, a by-pass valve assembly 456 and a by-pass valvecontrolling mechanism 458. These parts are interconnected by passagesand connected to another device in the overall system to provide anoperative structure. Afterburner fuel is admitted to housing 450 throughpassage 460 which is connected to a fuel outlet passage 462 by meteringorice 452. A normally closed solenoid operated valve 464 is locatedbetween passage 462 and conduit 74. Opening 466 provides a point atwhich a conduit may be connected to carry a working lluid to anotherdevice.

The by-pass valve assembly has a sleeve 468 lixedly mounted in bore 470of housing 450. An annular groove 472 located between the ends of thebore 470 communicates with an annular groove 474 on the interior of thesleeve by slots 476. An opening 478 connects annular groove 472 to aby-pass fuel return conduit 480, A second annular groove 482 is locatedat one end of bore 470 and a third annular groove 484 is located at theother end of said bore. These annular grooves 482 and 484 are incommunication with each end of the sleeve 468. A passage 486 connectsannular groove 482m passage 460 and passage 488 connects annular groove484 to passage 460. A by-pass valve 490 is slidably mounted in sleeve458 by ribs 492. rl`he end of the valve within sleeve 468 seats againsta circular ange 494 at one end of the sleeve and a circular flange 496on the valve seats on the other end of the sleeve. A stem 498 on thevalve 490 extends upward through a hole 500 in a rigid disk 502, whichis held betwen housing 450 and cover member 504. A spring 506 mountedaround stem 498 is seated at one end against a spring retaining cup 508in rigid disk 502 and at its other end against flange 496 of valve 498,biasing said valve to a closed position.

A bellows 510 is iixed at one end to rigid disk 502 and at its other endto a washer member 512 which is mounted near the end of stem 498. Twonuts 514 and 516 position said washer member on the valve stem. Theinterior of the bellows forms a chamber 8 with washer member 51'2 andrigid disk 502. This chamber communicates with annular groove 484through hole 580 in the rigid disk 502. The exterior ofthe bellows Slt),rigid disk 502, washer member 512 and cover member 504 form a chamber520 which is connected to valve 522 of the bypass valve controllingmechanism 458 by passages 524, 526, and 528. Annular groove 484 isconnected to pas- -in a recess 630 by bolts 632 6 sage 526 by passage530 which has a restricting orice 534 therein.

The by-pass valve controlling mechanism 4758 consists of a walking beam536 having various'fforces applied to regulate valve 522. A cover 538encloses this mechanism forming a chamber 540 which is connected to alower reference pressure by opening 542 and conduit 544. The walkingbeam is pivoted at 546. Valve 522 consists of a bushing 548 fixed inhousing 450 having an orifice 550 therein and a flow regulating part 552fixed on walking beam 536.

A spring 556 mounted between two spring retainers 558 and 560 is locatedunder valve 522 to bias said valve to a closed position. An adjustablescrew 562 is mounted in cover 538 to movably position spring retainer560. A spring 564 is mounted between the bushing 548 of valve 522 andwalking beam 536 to bias said valve to an open position. An adjustablestop 566 is mounted in housing 450 and extends'under a projection 568 onwalking beam 536 to control the amount of movement of said walking beam.

A cylinder member 568 is fixed to housing 450 in a recess 570 by bolts572 which pass through an annular ring 574 to clamp an outer extendingflange 576 of said cylinder member against said housing. A bellows 578is connected at one end to an inner circular flange 580 in the cylindermember and is connected at its other end to a disk 582 which is mountedon walking beam 536. The interior of bellows 578 is subjected to fuelinlet pressure from passage 460 by passage S84.

A second cylinder member 588 is fixed to cover 538 in a recess 590 bybolts 592 which pass through an annular ring 594 to clamp an outerextending ilange 596 of said cylinder member against said cover. Abellows 598 is connected at one end to an inner circular ange 660 in thecylinder member and is connected at its other end to a disk 602 which ismounted on walking beam 536. The interior of bellows 598 is subjected topressure from the fuel outlet 462 by passage 604. I

A third cylinder member 608 is fixed to cover 538 in a recess 610 bybolts 612 which pass through an annular ring 614 to clamp an outerextending flange 616 of said cylinder member against said cover. Abellows 618 is connected at one end to an inner circular flange 620 inthe cylinder member and is connected at its other end to a disk 622which is mounted on walking beam 536. The interior of bellows 618 issubjected to compressor inlet pressure by conduit 624. i

A fourth cylinder member 628 bushing 53.2l

is iixed to housing 450 which pass through an annular ring 634 to clampan outer extending `flange 636 of said cylinder member against saidhousing. A bellows 6381's connected at one end to an inner circular ange640 in the cylinder member and is connected at its other end to a disk642 which is mounted 'on walking beam 536. The interior of bellows 638is subjected to pressure from the attenuating valve assembly 454 bypassage 644.

The attenuating valve assembly 454 has a sleeve 648 which is xed in bore650 of housing 450. Snap ring 652 holds valve 654 of the assembly insleeve 648.v Sleeve 648 has anannular groove 656 which connects passage658 which has a bushing 660 with a restricting orifice 662 therein topassage 644. Passage 658 is connected to conduit 664. An orifice 666connects annular groove 656 to the center of sleeve 648. The lower endof valve 654 provides valve action by a contour 668 thereon which variesthe opening of orifice 666. The end of sleeve 648 is connected bypassage 670 to a conduit 672.y Valve 654 is rotated by a shaft 674 tovary the restriction formed by contour 668 and orice 666. p 'A fuelmeter of this type is also shown and claimed in co-pending applicationSerial No. 196,414 tiled November 18, 1950, now Patent No. 2,714,803,issued August .9, 1955. i

The exhaust nozzle actuator control 76 is a'd'eviceito.I

divert arremete the-exheustncaale actuating cylindersV 130 either toopen or to close the exhaust nozzle asV required., Compressedvair fromthe compressor 4 is delivered to the nozzle control 76 by conduit 236 toprovide theY operating pressure. Conduit 262 connects the nozzle controlto the side of the cylinders 130 which causes the nozzle 44 tol openwhenthe operating pressure is applied and conduit 266 connects the nozzlecontrol to the side of the cylinders 130 which causes the nozzle toclose when the operating pressure is applied. Turbine exhaust gas staticpressure which is delivered to the control 'i6 by conduit 79automatically actuates the nozzle control '76 to Aconnect conduit 230 toeither conduit 262 or 266. An exhaust nozzle actuator control of thistype is shown and claimed in co-pending application Serial No. 196,424filed November, 18, 1950now Patent No. 2,715,3ll, issued August.16,l955.

TheV igniter control 28 injccts an amount of fuel in addition to thatnormally supplied into combustion chamber S where itisignited resultingin flame propagation through the turbine into the afterburner forigniting a combustible mixture in the afterburner. Fuel is provided tothc igniter control 28 from the main fuel system by conduit 80 which hasa solenoid actuated shut-olf valve E52 connected therein. The ignitercontrol is connected by conduit 84 to conduit 74 which provides theactuating pressur-e to inject the additional fuel to provide ignition inthe afterburner.

The electrical system may include a temperature control amplier 86 whichduring afterburncr operation is sent a signal by thermocouples 88 whichsense turbine discharge temperature. Thermocouples 99 also sense turbinetemperature but send their signal to a temperature gage 92. Thisampliler when energized sends a signal to motor 300 of the fuel meter toattenuate fuel ow in accordance with turbine discharge temperature andcontrols the operation of a normally closed solenoid operated shut-olfvalve in the fuel meter. When a predetermined turbine dischargetemperature is reached, the motor 300 is operated to reduce the flow offuel to the afterburner ifsuch a reduction is possible; and when ahigher temperature is permissible and an increased afterourner fuel flowis possible, the motor 300 is operated to increase the flow of fuel tothe afterburner. in the L event a temperature is reached in theafterburner above another predetermined temperature and remains afterthe fuel ow to the afterburner has been reduced by the movement of motor300 the switch 93 will operate to permit the shut-olf valve in the fuelmeter to close of( the fuel ow to the afterburner. The afterburnerswitch 94- controls the amplifier 86, sets the motor operated valve 68,controls the fuel boosterpump 48, and controls the opening of normallyclosed solenoid actuated shut-off valve 82.

Operation Afterburner operation is initiated by placing switch 94 in itsvon position. This movement turns the teniperature controlamplier onwhich in turn opens a normallyy closed solenoidoperated shut-olf valvein the fuel meter and sends a signal to the afterburruer fuel meter forattenuating fuel flow therethrough. This movement of the switch alsoplaces motor operated valve 68 in open position, starts thepfuel boosterpump 48 and opens normally closed solenoid actuated shut-off valve 82.

The operation of the fuel booster pump forces fuel from the fuel tank 46through conduits S4 and 56 to the impeller 70 of the lfuel pump 50. Theopening of the motor operated valve 68 allows compressed air to beAdirected from the outlet of the engine compressor 4. throughconduits.230, 64 and 66 against turbine 58 to drive` the impeller 70. Theimpeller 70 then delivers fuel to Vthe afterburner fuel meter.

Since both the fuel/air ratio required by the turbine for operation `atthe conditions where afterburningfis used; and. the `fuel/airV ratiorequired in the afterburner are essentially constant, and since the gasflow throughy n may be approximately met by proportioning theafterburner fuel ilow to the engine fuel flow. As will be evident fromthe following description, if the fuel meter of Fig. 2 is used, theafterburner fuel flow will be proportioned to engine fuel flow withindesired limits, and this proportion may be more or less attenuated froma rich limit to a lean limit, manually or automatically, to finelycontrol some engine operating parameter such as turbine dischargetemperature.

Fuel supplied under pressure of impeller 70 flows into opening 114,through chamber 116, through orice 106 into outlet passage 118 andpasses by a normally closed solenoid actuated shut-off valve 120, whichis now open, to conduit '74 and fuel nozzles 26. The fuel pressuredifferential across the orifice 106 is controlled by by-pass valve 141which by-passes a portion of the fuel supplied by the pump 50. Since forany given operating condition the fuel flow supplied by the pump Sti tothe meter is a particular value, when valve 141 bypasses more of thisflow, there is less flow available to pass through the orifice 106. Theby-pass valve, which is held closed by spring 178, is opened by reducingthe fuel pressure in chamber 194, by virtue of the pressure differentialthus applied across bellows 181. The fuel pressure in chainv ber 194 isprovided through restricting orifice 163 which receives high-pressurefuel from chamber 116 through passages 139 and 146. The fuel pressure inchamber 194 is reduced by bleeding lluid through valve 196. When thevalve 196 is closed, there is no flow through said valve or throughrestriction 16S; therefore, the pressure in chamber 194 is the same asthe pressure in chamber 18% and consequently by-pass valve 141 is heldclosed by spring 178.

When valve 196 is opened, the resultant flow of fuel past said valve,which is supplied through restricting orifico 168, reduces the pressurein chamber 194 so that the by-pass valve opens. The amount of bleedingwhich occurs through valve 196 is determined by the action of walkingbeam 206. The action of walking beam 206 is regulated by balance of thefollowing pressures: unmetered fuel pressure from chamber 116 whichWorks against piston 236, spring 218, metered fuel pressure from passage118 which works against piston 248, and the pressure in chamber 292which works against piston 260. Equilibrium is reached in this hydraulicamplifier when the torque applied to the walking beam 206 by thepressure differential across the metering orifice 106 equals thecounter-torque applied to the walking beam by spring 218 and by thepressure in chamber 292.

A pressure difference to measure engine fuel flow is applied to theattenuating valve assembly 193 through conduits 287 and 298. The higherpressure of this fluel ow sense, which may be the fuel nozzle pressureas shown, is applied to conduit 287. The lower pressure, which may be adrain fuel pressure as shown, is applied to conduit 298. When therestricting area formed by contour 28S cooperating with orifice 290 islarge relative to the areaV of restricting orifice 2%, the pressure inchamber 292 approaches the high pressure of conduit 2.37. When therestricting area at orifice 290 is small relative to that of restrictingorice 296, the pressure in chamber 232 approaches the low pressure ofconduit 298. By rotating valve 275 the pressure in chamber 292 may beattenuated more or less relative to the fuel ilow indicating pressure inconduit 137. When valve 275 is rotated to reduce the area at orifice290, or when the pressure in conduit 287 decreases with lesser turbinefuel flows, the resultant lower pressures in chamber 292 require lesser,pressure differentials across orifice 106 to bring the walking beam 206to equilibrium and the afterburner fuelvflow is thus, reduced. In a likemanner an increase in the area of orifice 290 or an increase in pressurein conduit 287 reflecting `an increase in turbine fuel tiow will causean increase in afterburner fuel iiow. The valve 275 may be rotatedmanually, or by a suitable motor to vary the afterburner fuel ow withinthe limits established by the contour 288 and restricting orifice 296.These limits can be established so as to insure a combustible mixture inthe afterburner, and a suitable regulating means may be used to vary theafterburner fuel ow and control some engine operating parameter to adesired value. As shown, amplifier 86 measures turbine dischargetemperature by thermocouples 88 and varies afterburner fuel ow tocontrol said temperature at a desired value. If this is to be donemanually, one may look at gage 92 Aand move valve 275 manually until `adesired temperature is reached.

Since the fuel/air ratio required by the afterburner is substantiallyconstant, and since the gas iiow through the engine is for all practicalpurposes a unique function of the pressure rise across the compressor,it follows that the afterburner fuel ow requirements may beapproximately met by metering the fuel ow as some function of compressorpressure rise. As will be evident from the following description, if thefuel meter in Fig. 4 is used, the afterburner fuel will be proportionedas a function of compressor rise within desired limits, and thisproportion may be more or less attenuated from a rich limit to a leanlimit, manually or automatically, to nely control some engine operatingparameter such as turbine discharge temperature.

Fuel supplied under pressure of impeller 70 flows into pipe 312, throughthe balanced metering valve 334,. through opening 314 and by a normallyclosed solenoid operated shut-off valve 316, which is now open, toconduit 74 and fuel nozzles 26. The pressure drop across the meteringvalve 334 is controlled by the by-pass valve 414. The metering valve 334is a contoured valve so that the axial displacement of the valve effectsa predermined change in the area through which the afterburner fuel mustow. For any given operating condition the fuel iiow supplied by the pump50 to the meter is a particular value, and the by-pass valve 414maintains constant the pressure drop across the metering valve. When themetering valve 334 opens or closes, it changes the flow passing by saidvalve.

The bellows shown are equal in effective area and form a seal betweenthe fuel surrounding the valve andthe air pressures which are applied tothe diaphragm 350. Chamber 370 is connected by conduit 371 to compressorinlet pressure and chamber 362 is connected by passage 376 to compressordischarge pressure or a portion thereof as attenuated by valve 390.

1t can be seen that the pressure differential applied across thediaphragm 350, the attenuated compressor discharge pressure minuscompressor inlet pressure, isa particular proportion of the pressurerise across the compressor for the effective open area of orifice 398ixed by contour 460 of valve 390. For a given effective open area oforifice 39S, as the engine air ow increases the pressure rise across thecompressor also increases and is applied against diaphragm 350 to urgevalve 334-in i an open direction against spring 372. In a like manner,as engine air flow decreases the pressure rise across the compressoralso decreases and is applied against diaphragm 354i permitting thespring 372 to move valve 334 in closed direction, Then valve 334 assumesa position according to engine air ow and this position in accordancewith the contouring of valve 334 results in the proper afterburner fuelow.

A pressure difference to measure engine air flow is applied to theattenuating valve assembly 308 through conduits 395 and Sti-i. Thehigher pressure of this air flow sense, which may be the compressordischarge pressure as shown, is applied to conduit 395. The lowerpressure, which may be compressor inlet pressure as shown, is applied toconduit 404. When the restricting area formed by contour 400 cooperatingwith orifice 398 is large relative to the area of restriction 397, thepressure in chamber 362 approaches the low pressure of conduit 404. Whenthe restricting area at orifice 398 is small relative to that ofrestriction 397, the pressure in chamber 362 approaches the highpressure of conduit 395. By rotating the valve 390 the pressure inchamber 362 may be attenuated more or less relative to the air liowindicating pressure in conduit 395. When valve 390 is rotated to reducethe area at orifice 398, the resultant higher pressures in chamber 362urge valve 334 in an open direction against spring 372. In a like manneran increase in the area of orifice 398 will cause a reduction inafterburner fuel liow by permitting valve 334 to move in a closeddirection.

The valve 390 may be rotated manually, or by a suitable motor, to Varythe afterburner fuel flow within limits established by the contour 404iand orifice 39S. These limits can be established so as to insure acombustible mixture in the afterburner, and a suitable regulating meansmay be used to vary the afterburner fuel iiow and control some engineoperating parameter to a desired value. As mentioned in the operation ofthe fuel meter shown in Fig. 2, amplifier 86 along with thermocouples 88provide a suitable regulating means, and if thevalve is to be rotatedmanually a gage 92 is provided with which to read the temperature at anydesired point in the engine.

As will be evident from the following description, if the fuel meter inFig. 6 is used, the afterburner fuel will be proportioned as a functionof compressor rise within desired limits, and this proportion may bemore or less attenuated from the rich limit to the lean limit, manuallyor automatically, to finely control some engine operating parameter suchas turbine discharge temperature.

Fuel supplied under pressure of impeller 70 ows into passage 460,through orifice 452 into outlet passage 462 and passes by a normallyclosed solenoid actuated shutoff valve 464, which is now open, toconduit 74 and fuel nozzles 26. The fuel pressure differential acrossthe orice 452 is controlled by by-pass valve 490 which bypasses aportion of the fuel supplied by the pump 50. Since for any givenoperating condition the fuel flow supplied by thev pump 50 is aparticular value, when valve 49@ by-passes more of this fuel, there isless flow available to pass through the orifice 452. The by-pass valvewhich is held closed by spring 506 is opened by reducing the fuelpressure in chamber 520, by virtue of the pressure differential thusapplied across bellows 510. The fuel pressure in chamber 520 is providedthrough restricting orifice 534 which receives high pressure fuel fromannular groove 484 through passages 538, 526, and 524. Chamber 518receives high pressure fuel from annular groove 484 through hole Sti@ inrigid disk 592. The fuel pressure in chamber 520 is reduced by bleedingthe fluid through valve 522. When valve 522 Vis closed, there is no liowthrough said valve or through restriction 534; therefore the pressure-in'chamber 528 is the same as the pres/surerinchamber 518 and consequentlyluy-pass valve 490 is held closed by spring 506.

When Valve 522 is open, the resultant flow of fuel past said valve,which is supplied through restricting oritice 534, reduces the pressurein chamber 528 so that the by-pass valve opens. The amount of bleedingwhich occurs through valve 522 is determined by the action of walkingbeam 536. The action of walking beam 536 is regulated by balance of thefollowingpressures: spring 564, unmetered fuel pressure from passage 468which is applied to bellows 578, the pressure in annular groove 656which is applied to bellows 638, spring 556, metered fuel pressure frompassage 462 which is applied to bellows 598, and the pressure which isapplied to bellows 618. Equilibrium is reached iu this hydraulicamplifier when the torque applied to the walking beam 536 by thepressure differential across the metering orifice 452 and by 1l spring564 equal the countertorque applied to the walking beam by the pressuredifferential between the pressure in bellows 638 and the pressure inbellows 618 and by spring 556.

To measure engine air ow, the difference in pressures of two stations inthe gas flow path of the engine is ap plied to the attenuating valveassembly 454 through conduits 664 and 672. The higher pressure of thisair flow sense, which may be compressor discharge pressure as shown, isapplied to conduit 664. The lower pressure, which may be compressorinlet pressure as shown, is applied to conduit 672, and is also appliedto bellows 618 by conduit 624. When the restricting area formed bycontour 663 cooperating with orifice 666 is large relative to the areaof restriction 662, the pressure in bellows 638 approaches the lowpressure of conduit 672. When the restricting area at orice 666 is smallrelative to that of restriction v662, the pressure in bellows 638approaches the high pressure of conduit 664. By rotating the valve 654the pressure in bellows 638 is thus attenuated more or less relative tothe air tlow indicating pressure in conduit 664. When valve 654 isrotated to reduce the area at orii'ice 666, or when the pressuredifference between conduit 664 and the conduits 672 and 624 increaseswith greater engine air flows, the resultant increase in differencebetween the pressure in bellows 638 and the pressure in bellows 618requires higher pressure difierentials across orifice 452 to bring thewalking beam 536 to equilibrium, thereby increasing the afterburner fuelflow. ln a like manner an increase in the area of orifice 666, or adecrease in the pressure difference between conduit 664 and the conduits672 and 624 reiiecting a lesser engine air ow, will cause a decrease inafterburner fuel flow.

The valve 654 may be rotated manually, or by automatic means, to varythe afterburner fuel flow within limits established by the contour 668and oriiice 666 as mentioned in the operation of the fuel meter shown inFig. 2 and Fig. 4.

The opening of the normally closed solenoid actuated shut-off valve 82permits a source of fuel to be supplied to the igniter control 28through conduit 8d. The pressure of the fuel in conduit 74 istransferred to the igniter by conduit 84 which pressure permits fuelwhich has passed normally closed solenoid actuated shut-olf valve 82 tobe injected from the igniter control into a combustion chamber 8.Ignition of the injected fuel results in llame propagation through theturbine to the tail pipe resulting in ignition in the afterburner of thefuel being introduced through nozzles 26.

The ignition of fuel within the afterburner results in an increase inturbine exhaust gas pressure above that normally obtained Withoutafterburning. This increase in pressure is transmitted to the exhaustnozzle actuator control through conduit 79. The control 76 in accordancewith this pressure directs compressor discharge air from conduit 236through conduit 262 tothe side of the cylinders nearest the nozzle whichcauses nozzle 44 to open. The pressure in this conduit 262. istransmitted by conduit 9S to a normally closed pressure switch-96 in theelectrical line tothe normally closed solenoid actuated shut-ofi valve82 which opens said switch thereby closing the shut-olf valve S2preventing a flow of fuel to the igniter control 28.

To cease operation of the afterburner the afterburner switch 94 isturned to itsffoi position. This turns the temperature control amplifier86 olf thereby turning off 196,425 tiled November 18,

a supply ofcurrent to the normally closed solenoid oper ated; shut-olicvalve in the fuel meter and' the normally closed 'solenoid actuatedshut-ott valve 82 in conduit The movementof the switch to the oilposition also closes Vthe motor operated valve 68 and turns otf'theafterburner fuel booster pump 48. it will be seen that with no fuelliow, combustion cannot be maintained in the afterburner. This decreasein afterburner pressure is transmitted to the exhaust nozzle actuatorcontrol thereby directing compressed air through conduit 266 fromconduit 231i) to the side of the cylinder 13b farthest from the nozzlewhich causes nozzle 44 to close. The reduction of pressurein conduit 262is conveyed to normally closed pressure switch 96 by conduit 98 therebypermitting the switch to be closed to permit current to pass to valve S2upon the next starting of the afterburner.

Although specific fuel meters have been shown and described herein forpurpose of illustration, it will be evident to those skilled in the artthat the invention is capable of various" other modications andadaptations within the scope of the appended claim. The control systemfor an afterburner as shown in this application is shown and claimedv inco-pending application Serial No. 1950, now Patent No. 2,789,054, issuedFebruary 5, 1957.

I claim:V

A fuel meter having in combination a housing, an inletpassage, ameteringorifice, an outlet passage, a bypass valve connected to saidinlet passage, liexible means in said housing forming two chambers, saidby-pass valve being connected to said flexible means, each chamber beingconnected to said inlet passage, spring means biasing said by-pass valveto a closed position,l a restriction in the connection to one chamber,first means responsive to an engine operating variable for operatingsaid by-pass valve, said first means also being responsive to thepressure-drop across saidv orifice, and means responsive to an engineoperating variable for attenuating the effect of the ilrst engineoperating variable, said first means including a lever and a valve, saidvalve operating to open said chamber having a restriction in itsconnection to bleed;

References Cited in the tile of this patent UNTED STATES' PATENTS2,095,991 Lysholm Oct. 19, 1937 2,422,808 Stokes June 24, 1947 2,441,948Atkinson May 25, 1948 2,457,595 Orr Dec. 23, 1948 2,498,939 Bobier Feb.28, 1950 2,564,107 Holley Aug. 14, 1951 2,566,373 Redding Sept. 4, 19512,570,591 Price Oct. 9, 1951 2,638,992 Lundquist et al.v May 19, 19532,640,316 Neal June 2, 1953 2,667,743A Lee Feb. 2, 1954 2,668,416 LeeFeb. 9, 1954 2,675,674 ALee lApr. 20, 1954 2,688,841` Decher et al.Sept. 14, 1954 2,700,275r Chandler et al Jan. 25, 1955 2,737,015 WrightMar. 6, 1956 FOREIGN PATENTS 5.76,*243v Great Britain Mar. 26, 1946941,556 France July 19, 1948

